basics of reactor physics to study the futures of nuclear

Basics of Reactor Physics to study the Futures of Nuclear Energy

Séminaire Daniel DAUTREPPE

Demain l’énergie Grenoble

08/12/2016

Xavier Doligez Institut de physique nucléaire d’Orsay

[email protected]

A nuclear power plant ?

A quite simple process : - like most of electrical power plant Pressurized Water Reactor & Boiling Water

Reactor represent more than 81% of the existing reactors

There are 435 reactors operated in the world

~ 10% of electricity (2 500 TWh/y) ~ 5% of primary energy

Thermal efficiency ~33%

Nuclear energy in France

19 power plants 58 reactors 65 millions of inhabitants 78% of french electricity

One reactor for 1,1 millions of inahabitants

A single technolodgy: Pressurized water reactors (PWR) Newest : Civaux 2 (1999) Oldest : Fessenheim (1&2) (1977) 1 under construction (EPR de Flamanville) – Planned for 2012 ; full operation 201?

Nuclear energy is very (very) concentrated

30 tons of enriched uranium ~ 1,8 Mtons of coal

Which geographical framework for the debate ? - Germany : quit nuclear energy ASAP - Poland : want to build two reactors ASAP - Italy : no return to nuclear energy - France : Energy transition law (willing of reduction)

… But Construction of 2 EPR in UK 3

For the future and in the world

WWF scenario : 0 TWh in 2050 Oil industry scenario (Exon & Total) : Stable in 2050 ; translation from Europe to Asia IAE scenario : between x2 (NPS) and x3 (450) in 2035 IIASA Scenario (type 450) : x 16 in 2100

Hypothesis : 3 constraints - Climate (2°C limitation) - Energy production (20 Gtep) - Consommation share (4/2/1) Adjustment : - Nuclear share in 2050

Issues and technologies are strongly dependent of the global nuclear evolution 4

Outline

1/ Reactor physics 101 Neutron interaction with matter Why pressurized water reactors ? 2/ Nuclear waste What’s that ? The CIGEO project The plutonium issue 3/ Natural uranium resources The limits of current technology Transition towards sodium fast reactors 4/ What about today ? Nuclear costs Challenges for PWR ASTRID project

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Fission and criticality

Neutrons produced by fission can induce fission and provoque a chain reaction

In a reactor the number of fission is (and has to be) constant critical sytem

Neutrons interact with nucleus… not atoms !! Natural uranium : 235U (0,7%) and 238U (99,3%)

Fission of heavy nuclei release between 2 and 3 neutrons with a huge quantity of energy (200MeV) and produces two fission fragments. Fission is provoqued by a neutron absorption (neutron balance = +1.5)

Fissionable with any kind of neutrons

Fissionable with energetic neutrons Kinetic energy of fission neutron from

is not sufficient

No chain reaction are possible with U-238 6

Neutron interaction with matter and criticality

7

Neutrons’ range are huge in comparison to their typical size


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If a neutron interacts with a nucleus, serval options are possible : 1/ Elastique scattering : the neutron gives a part of its energy to the target


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If a neutron interacts with a nucleus, several options are possible : 1/ Elastic scattering : the neutron gives a part of its energy to the target 2/ Neutron absorption : the neutron is captured by the nucleus leading to a new one (radioactive)

If the nucleus is fissile (235U, 239Pu, …), this absoption can lead to fission Neutron balance = +1,5 neutrons

If there is no fission, the absorption is then a sterile capture Neutron balance = -1 neutron


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Microscopic cross section quantifies the probability of neutron interaction with a given nucleus

Neutrons produced by fission


Everything happens like if the nucleus radius is a function of the neutron kinetic energy The slower the neutrons are, the higher is the relative radius of 235U

To maximise the fission probability by neutron interaction, one should use slow neutrons Unfortunately, neutrons emmited by fission are fast


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Fisison and emission of 2,5 neutrons

The water inside reactors is nedeed to Cool down the fuel (and produce steam) Slow down the neutrons

Moderator (water)

If the reactor is critical, one and only one neutron emitted by fission induces another fission


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Pressurized water reactors

Compromise between enrichment and reactor technology Enriched Uranium (between 3 et 5%) Each assembly is composed by 264 fuel pins (17 x 17)

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The fission

Number of protons

Number of neutrons

Fissioning nuclei (U-235; Pu-239)

Fission products are then (very) radioactive - Even if the reactor is shut dowwn, there is a huge heat production Safety issue : to maintain the reactor cooling whatever happens - No reactor without wastes

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The fission…. Or not ?

Number of protons

Fuel irradiation produces heavy nuclei - Plutonium is produced by 238U neutron capture - Elements heavier than plutonium arecalled minor acinides 16

Nuclear wastes

“96 % of the nuclear spent fuel is reusable”

Wastes : « Radioactive wastes are radioactive matter which NO further utilization is planed » French law (2006)

U nat U enr -Fission Product -100% U et Pu -100% Np, Am, Cm

Open cycle : ex USA

U nat U enr -Fission Product -0,1% U et Pu -100% Np, Am, Cm

« Closed » cycle : ex France

Pu monorecycling U & Pu

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How to qualify nuclear waste ?

Radiotoxicity (Sievert) : a way to quantify the impact of nuclear wastes

Time in year

Ra

dio

toxi

city

(u

.a.)

Spent UOx after 5 years of cooling

The Sievert is a unit built to quantify the damages of radiation on the human body Hypothesis of calculation : all radioisotopes have scattered into drinkable water Source term : not a real meaning but is a good way to compare different contributions

Regarding your strategy the radioactivity you have to deal with in the storage is greatly diminished

The goal of storage is to limit the diffusion of long living wastes (T ~300 years) However, the heat is due to FP (T~30 years)

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CIGEO

CIGEO concerns only the waste already produced and the one to be produced of the current reactors

Already produced

After 40 years with reprocessing

After 40 years wihtout reprocessing

CIGEO Capacity

HA-LV 5 700 m3 8 000 m3 93 500 m3 10 000 m3

MA-VL 57 500 m3 67 500 m3 59 000 m3 70 000 m3

CIGEO invent :

In the end, the total surface at the surface would be 15 km²

Future generation involvement YES NO

Pros For a « sustainable » nuclear

For waste repository X

X

Opponent Against a « sustainable » nuclear

Against waste repository

X X

The nuclear debate paradox

“There is solution for our nuclear waste”

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The use of Pu in current reactor to decrease radiotoxicity

Time (year)

Ra

dio

toxi

cité

(u

.a.)

Open cycle

Plutonium can replace uranium Construction of Mox fuel in order to save natural uranium To burn plutonium in order to decrease the radiotoxicity of Pu 7 Uox spent fuel assembly produce enough Pu for 1 Mox assembly Comparison of 8 Uox spent fuel and 1 Mox spent fluel + 7 glasses

Spent MOX fuel contains Pu It is not a waste… temporally stored for further use… (if there are uranium tension) 20

Plutonium valorization

238U+n 239U 239Np 239Pu Fertile Fissile

Based on the use of 235-U (0,7% of the natural uranium) - 1 ton of matter that have actually fissionned - 27 tons of enriched uranium - 200 tons natural uranium - improving the enrichment process - recycling uranium - recycling plutonium

PWR

1 Gwe.year

130 tons of Unat/Gwe.y

It is possible to improve this consumption by a factor 130 !

The mass of plutonium inside the reactor is constant 1 ton of depleted uranium for 1 Gwe.an

300 000 tons of depleted uranium in France 5000 years of electricity

For the chain reaction, 2 neutrons are needed - For the fission - For the plutonium production

New technology : SFR

For the french park 1000 tons are needed (we’ve got 300 tons)

Sodium cooled fast reactors

Superphénix example

Cooling: liquid sodium - cheep - Industrial know how - Atm. pressure

However, sodium is not stable with air neither with water

- Internal

Improved safety

Increase of construction costs

SPX shut down (and dismentling) in 1996 by French government decision

Economic viability

Natural uranium price ($)

Electricity price ($)

Investment for the reactor construction

Breeder

“Maximum” natural price that defines the ultimate resources

Economic viability, with error bars !

Natural uranium price ($)

Electricity price ($)

Breeder

“Maximum” natural : From 130 $/kg until > 1000$/kg

Huge uncertainty regarding the natural uranium available that will justify the change of a new technology

Today : 285 Gwe (Full power equivalent) 60 000 tons of natural uranium/years Estimated ressources 10 – 23 millions of tons

The nuclear energy in the economy

Unknown resources - Phosphates (~ 7.3 Mt) - Sea water (~4.5 Gt)

Today :

- 45 000 tons of natural uranium / year - Cigar lake : planned for 2007 ; open in 2014 Nominal production : 10 900 t/years

Beware of simple arguments !

0

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année

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Nuclear demand

400 $/kg

200t/(GWe.an) 130t/(GWe.an)

Cumulative uranium consumption

< 130$/kg < 260 $/kg

Identified 5,9 Mt 7,6 Mt

Speculative 6,5 Mt 6,9 Mt

Plutonium issue :

Due to the fast neutron spectrum, the global amount of plutonium in SFR is very important Phase out considerations

Waste produced ~ global inventory / 1000

It takes 1000 years to produce the waste that are as “nasty” as the fuel

A small sum-up

A global increase of the nuclear energy ?

YES NO

Current technology (PWR, BWR) is consuming too much natural uranium

Need to change towards Fast reactors (huge plutonium is needed to start up)

Plutonium is a valuable and expensive matter

We don’t need uranium savings Current reactors are satisfying if operated in

safe conditions Plutonium is the principal waste

More than factor 8 Less than a factor 2

Take home messages :

Nuclear current technology is based on the fission of 235U The only natural fissionable nuclei

Natural uranium resources allow around a century of nuclear operation at current level 1 GWe = 1 ton of fission = 30 tons of enriched uranium = 130 tons of natural uranium (at best)

Regarding the strategy, Plutonium is a valuable matter or a painful waste

It is possible to operate a nuclear fleet without any needs of natural resources Transition to SFR

27

Different cost evaluations

Theory

€

Construction Operation

Dismantling + waste repository

Total costs

Beware : one euro today is different from on euro in 2050

Production ~ 440 TWh (for 60 years)

44 €/MWh 110 €/MWh

«coût comptable »

Construction time : 5 years Discount rate : 5% Reactor costs : 3 G€

Construction time : 10 years Disctount rate : 8% Reactor cost : 9G€

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Discount rate: a way to reduce future expenses uncertainties

Price x100

Cost+10

Different figures from litterature

Taux d’actualisation = 0% Taux d’actualisation = 5%

Coût comptable Coût courant économique

Cout ARENH Coût courant économique (2014)

33,4 €/MWh (€2010) 49,5 €/MWh (€2010) 42 €/MWh 59,8 €/MWh (€2014)

Levelised cost of elecctricity (LCOE)

EDF selling price to other producers

French government = share holders or consumers ?

Take into account future reactors (capital valorization)

Big volume market price2015 ~ 35 €/MWh

Different cost evaluations

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French reference scenario

Making efforts today to keep the possible choice tomorrow (Very) long term strategy The plutonium is a valuable matter

What if ? - There is a delay in fast reactor deployment ?

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An ambitious project for French fast reactors

ASTRID (CEA) – 600 MWe Goals: Insure « a passive » safety of the core If the temperature increases, the chain reaction has to stop A very ambitious fuel loading plan From the French law in 2006 : a road map - 2020 : Building a GENIV prototype - 2012 : CEA report on the 2006 law - Tome 3 : dedicated to ASTRID conception

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Because we are in Grenoble…

A very innovative project that redefine nuclear systems concept : Molten Salt Reactors

Liquid fuel Thorium molten salt

• High temperature

Fast neutron spectrum • Uranium breeding

• Minor actinides burning

In-line reprocessing

The concept has been proven experimentaly, (as many reactor concepts) but remains too inovative for a near future

232Th+n 233Th 233Pa 233U Fertile Fissile

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General conclusions

Nuclear is an energy source for the XXI century ! Where ? Asia, Eastern Europe, Latin America ? Africa ? Middle East ? Regarding the different objectives scenarios predict basically every possibility for nuclear future But only politics take actions Nuclear power deployment will be driven by Asia A crisis on the uranium market would justify the deployment of new type of reactors In that case, the plutonium is a valuable matter that should be stored At the opposite, it could become the major issue of nuclear waste The are lots of uncertainties and the choices have to be anticipated The Pu needed for one SFR the total production of 40 years of PWR operation The French strategy is to make efforts now to have a choice tomorrow Is it compatible with the energy transition ?

Thank you for your attention

basics of reactor physics to study the futures of nuclear

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